Apparatus for making foundry moulds

ABSTRACT

Apparatus for continuous, high speed production of foundry mould parts by pressing them from a continuous bed of foundry sand mix which is based on a curable binder, pressing of the part being carried out at a time when the mix has adequate plastic flowability for pressure moulding and adequate potential curability to assure a strong, rigid cured product. Advantageous embodiments include curing means operating in conjunction with the pressing means.

RELATED APPLICATION

This application is a continuation-in-part of our copending applicationSer. No. 154,763, filed June 21, 1971, and now U.S. Pat. No. 3,739,834.

BACKGROUND OF THE INVENTION

In present foundry practice, moulds are made in a number of ways,including the production of green sand moulds and the production of"shell moulds". However, despite long acceptance and continuousrefinement, including in recent years various approaches designed toautomate such practices, the practices of the prior art have had anumber of drawbacks, and these have become more critical in recent yearsbecause of the need for improving working conditions in the foundriesand the need to make moulds more rapidly with a lower manpowerrequirement.

Much of the requirement for foundry moulds has .[.here tofore.]..Iadd.heretofore .Iaddend.been met by making green sand moulds,following procedures usually requiring use of sea coal and providing amould which is not cured in the sense that it has adequate strength toallow extensive handling. The use of .[.seal.]. .Iadd.sea .Iaddend.coalhas always been objectionable because that material is dirty,contributing a great part, if not the primary part, of the dirt commonin foundries today. The weak, uncured nature of green .[.snad.]..Iadd.sand .Iaddend.moulds has also been a seriously limiting factor,even in the recently developed automatic moulding systems, since suchmoulds cannot be handled extensively or transported in the usual sense,as by trucks and the like, and the green sand moulds therefore must bemade at the location where they are to be used. The practice of usinggreen sand moulds has other disadvantages, including limitations on thedimensional accuracy of the moulds, the need for metal moulding flasksto prevent metal run-out, a relatively high time and labor requirementin mould production, excessive raw material storage requirements,including storage for sea coal, and excessive sand burn-on duringcasting, with attendant excessive time requirements in the cleaningroom.

While shell mould practices offer some advantages, including eliminationof sea coal and the production of moulds which are cured and thereforehave .[.adeuqate.]. .Iadd.adequate .Iaddend. strength to withstandconsiderable handling, shell moulds have only a relatively limitedapplicability and cannot be adopted as an extensive replacement forgreen sand moulds and are subject to the disadvantages of high patterntime and cost and the tendency for the shell mould itself to warp.

The method disclosed in our aforementioned copending applicationprovides for high rate, automated production from dry sand formulationsof fully cured foundry moulds, avoiding the use of sea coal and otherobjectionable ingredients, with the cured moulds having greaterdimensional accuracy and being sufficiently strong to withstand handlingand transportation, the moulds requiring less sand and shorter andeasier operations in the cleaning room than is the case with castingsfrom green sand moulds. A general object of the present invention is toprovide apparatus for carrying out that method.

Another object is to provide a mould pressing apparatus whereinoperation of the apparatus to shape a portion of a bed of sand mixaccording to a pattern also serves to sever the pressed mould part fromthe bed of sand mix.

A further object is to devise such an apparatus including means forcuring the pressed mould parts.

Still another object is to provide an apparatus capable of shaping andcuring mould parts on a continuous, automated, high rate basis.

SUMMARY OF THE INVENTION

Stated broadly, apparatus according to the invention comprise a conveyorextending generally horizontally from a mix depositing station through amould part pressing station; means at the pressing station forsimultaneously pressing an increment of a bed of sand mix on theconveyor into the shape desired for the mould part and severing thatincrement from the bed of sand mix; and means for driving the conveyorto present a new portion of the bed of sand mix at the pressing stationand advance the formed and severed mould part away from the pressingstation. In particularly advantageous embodiments, the pressing meansoperates in conjunction with curing means, the conveyor serving topresent a number of the pressed mould parts to the curing means forsimultaneous curing treatment each time the pressing means is operatedto sever and form a new mould part.

In order that the manner in which the foregoing and other objects areachieved according to the invention can be understood in detail,particularly advantageous embodiments thereof will be described withreference to the accompanying drawings, which form a part of theoriginal disclosure hereof, and wherein:

FIG. 1 is a semi-diagrammatic illustration of apparatus according to oneembodiment;

FIG. 2 is a bottom plan view of a pressing die employed in the apparatusof FIG. 1;

FIG. 3 is a sectional view taken generally on line 3--3, FIG. 2;

FIG. 4 is a semi-diagrammatic illustration of apparatus according toanother embodiment;

FIG. 5 is a semi-diagrammatic view illustrating a modified form of theapparatus of FIG. 4;

FIG. 6 is a semi-diagrammatic view of an apparatus similar to that ofFIG. 4 but adapted for simultaneous production of both the cope and dragfor a complete mould;

FIG. 7 is a side elevational view of an apparatus generally in accordwith FIG. 4;

FIG. 8 is a top plan elevational view of the apparatus of FIG. 7, withparts removed for clarity of illustration.

FIGS. 9 and 10 are enlarged transverse sectional views takenrespectively on lines 9--9 and 10--10, FIG. 7;

FIG. 11 is a fragmentary side elevational view illustrating the drivemechanism for the conveyor forming part of the apparatus of FIG. 7;

FIG. 12 is a side elevational view of a feed hopper and relatedmechanism employed in the apparatus of FIG. 7;

FIG. 13 is a horizontal sectional view taken on line 13--13, FIG. 12;

FIG. 14 is an enlarged side elevational view, with parts broken away forclarity of illustration, of the forming press employed in the apparatusof FIG. 7;

FIG. 15 is a view, mainly in side elevation, taken generally on line15--15, FIG. 14

FIG. 16 is a fragmentary horizontal sectional view taken generally online 16--16, FIG. 15;

FIG. 17 is a side elevational view of curing apparatus forming part ofthe apparatus of FIG. 7;

FIG. 18 is a transverse sectional view taken on line 18--18, FIG. 17;

FIG. 19 is a fragmentary plan elevational view taken on line 19--19,FIG. 18; and

FIG. 20 is an enlarged fragmentary side elevational view of a lock-downmechanism embodied in the apparatus of FIGS. 17-19.

THE METHOD CARRIED OUT BY THE APPARATUS

Apparatus according to the invention first establishes on a conveyor abed of a mix including dry sand and a curable binder, advances the bedto a pressing station, forces a pattern into the bed while the bed issupported so as to press the mix into the shape desired for the cope ordrag of the mould, and at the same time separate the pressed mould part(cope or drag) from the uncompressed mix, then advances the mould partto a curing station where the part is cured to provide adequate rigidityfor handling. The mix employed is of such plastic nature as to bemouldable by pressing under acceptable conditions of pressure and time,and is also characterized by curability after being shaped by thepressing operation. Support of the bed of mouldable sand mix istypically accomplished by a conveyor belt, with a supporting elementbacking up the belt at the forming station, and with the shaping pressand belt operated at speeds to give, e.g., a production rate of up to 20mould parts per minute.

The initial composition or sand mix must be mouldable under conditionsof reasonable pressure and time, and must retain this characteristic fora period of time adequate to allow the mix to be prepared, the bed to beformed, and the bed to be advanced to the pressing station. Mouldabilitycan be characterized as requiring both plastic flowability, so that themix will respond to the pressing operation, and early toughness ortenacity, to assure that the pressed part will retain its shape as anintegral body with precise dimensions and surfaces. In addition, the mixmust be capable of being cured under reasonable conditions of time,e.g., preferably not exceeding 15 min. and in all events not more than60 min., and temperature, e.g., from room temperature to 600° F. It isalso necessary that the binder material employed be of such nature thatthe cured binder material will be destroyed or burned out during castingof metal in the mould, and that the entire mix be of such nature thatevolution of nitrogen and hydrogen be minimized when the mould is incontact with the liquid metal during casting.

A wide variety of binder materials can be employed, including the alkalimetal silicate binders, the curable polymeric materials, core oilbinders, and mixed binder systems, e.g., systems comprising both acurable polymer and a core oil, and systems comprising both a silicateand a polymeric material. Certain binder materials are especiallyadvantageous because they provide both excellent characteristics forpressing of the mould part and economy as to cost of materials and costof curing. Thus, formulations employing an alkali metal silicate,particularly sodium silicate, offer special advantages, as doformulations employing as the binder material a composition comprisingboth an isocyanate and an oil-modified alkyd resin.

Formulation of the initial mix can be based on a binder material whichcures by a catalyzed reaction, in which case suitable proportions of acatalyst or catalysts are included in the mix or subsequentlyintroduced, or on binder materials cured solely by application of heator by gassing the pressed mould part with a gaseous curing agent oragents. In all instances, the formulation is such that, at the timepressing is to be accomplished, the mix has adequate plastic flowabilityto be pressed to shape, an adequate inter-particle plastic adhesion toassure that the shape imparted during pressing will be retainedprecisely, and enough residual cure capability to assure that, afterfinal curing, the mould part will have adequate strength for handlingand adequate hot strength for casting. Accordingly, in any applicationof the apparatus, the time .[.preiod.]. .Iadd.period .Iaddend.betweencompletion of mixing and presentation of the bed or layer at thepressing station must be selected, in view of the cure rate whichcharacterizes the binder material employed, so that, at the time themould part is pressed, progressive curing will not have proceeded so faras to create a relatively rigid inter-particle bond which would bedisrupted by the pressing step and then could not be re-established byfurther curing of the binder material.

Curable polymeric materials useful according to the invention are thethermoset resins, including the phenolic resins, the urea-furan resins,the water soluble modified resorcinol resins, furfurylalcohol-formaldehyde resins, and the isocyanate resin systems including,in addition to the isocyanate, a hydroxyl-containing coreactant, e.g., ahydroxyl-containing drying oil. Polymeric materials based on an aromaticpolyisocyanate, an oil-modified alkyd resin and a suitable catalyst orcatalysts are particularly effective. Such materials are described, forexample, in U.S. Pat. Nos. 3,255,500, issued June 14, 1965, to James J.Engel and Vernon L. Guyer, and 3,426,831, issued Feb. 11, 1969, to JanisRobins and Robert J. Schafer.

Suitable alkali metal silicate binder materials are those based onaqueous solutions or dispersions containing at least 10 percent byweight of the alkali metal silicate and having a silica to alkali metaloxide weight ratio in the range of 0.5:1 - 5:1. Sodium silicatesolutions in which the SiO₂ :Na₂ O weight ratio is 1:1 - 3.5:1 areparticularly useful. The alkali metal silicate content of the aqueousmaterial can be as high as 65% by weight, with contents of at least 30percent by weight being particularly effective. Mixes based on alkalimetal silicate binder materials can be cured by evaporation of water, byapplication of heat, by gassing with an acid gas such as CO₂, or byincluding in the binder material a curing catalyst such as an aqueousacid solution or a latent acid catalyst, e.g., a glycerol mono-, di-, ortri-acetate. Conventional additives can be included, such as theorganosilicones or alumina employed to improve collapsibility orshake-out characteristics; the alkali metal siliconates and like agentsused to improve resistance to moisture; and kerosene, for bothlubricating and improving moisture resistance.

With all binder materials according to the invention, it is desirable tominimize the amount of binder in order to reduce the raw materials cost.One way in which this is advantageously accomplished is by use of aninexpensive compatible extender for the primary binder material.Particularly useful extenders for the polymeric binders are theso-called CTLA hydrocarbon polymer oils, prepared generally as describedin U.S. Pat. No. 2,861,966, issued Nov. 25, 1958, to Joseph L. Betts andJohn P. Thorn. Such polymer oils have a Staudinger molecular weight of200-1000, an iodine number of 240-320, and a boiling point in the rangeof 400°-1,000° F. Also useful as extenders are other core oils preparedby combining polymerized unsaturated hydrocarbons and, e.g., a dryingoil.

When the binder employed is one which does not in itself provideadequate early toughness, additional additive materials are employed forthis purpose. Such materials include cereal products, e.g., maize (corn)flours and such flours which have been partially dextrinized; woodflour; fire clay; china clay; bentonite; fine sand; bank sand; silicaflour; and iron oxide.

In selecting formulations for use according to the invention, care mustbe taken to assure that the sand mix will retain its mouldability for aperiod of time adequate to accomplish the manipulative steps necessaryto press the mould part and, particularly, to assure that curing of thebinder does not progress so far, before pressing is done, that theinter-particle bond will be defeated by the pressing step. One way todetermine suitablity of a sand mix for use according to the invention isto measure the change in density of standard rammed test specimens overthat period of time required for mixing the materials, delivering themix and forming the bed, presenting the bed at the pressing station, andcarrying out pressing. That time period will of course vary, dependingupon, e.g., apparatus details. Assuming the use of continuous mixingapparatus for production of the sand mix, and an endless belt apparatuson which the bed is formed and which advances the bed to the pressingstation, typical time periods from start of mixing to completion ofpressing can be on the order of 2-20 mins., and for illustrativepurposes can be taken as 10 mins. In testing sand mixes for suitability,cylindrical specimens 2 inches long and 2 inches in diameter, rammed 3times with a 14 lb. weight, according to AFS Standard Foundry SandMixture Test Specimen, pages 4-4 through 4-11 of the Foundry SandHandbook, 7th Ed., 1963, published by the American Foundrymen's Society,can be employed. Density comparisons are made between a specimen from afirst sample, rammed immediately after mixing is completed, and aspecimen prepared from a second sample, rammed at a given time (e.g., 6min., when the mixing time is 4 min., to give the 10 min. test period)after mixing is completed. A density variation between the two specimensnot exceeding 6 percent, and advantageously not exceeding 4 percent, formost compositions employing a polymeric binder material or an alkalimetal .[.slicate.]. .Iadd.silicate .Iaddend.binder material, and 14percent for oil sand mixes, indicates that the composition is suitableaccording to the invention.

When progressively curable polymeric binder materials are employed,suitability according to the foregoing test procedure can be achievedwith proportions of binder material ranging up to 10 percent of theweight of sand employed. Particularly satisfactory results are obtainedwith binder materials comprising both an amount of a polyisocyanate-oilmodified alkyd resin combination equal to 0.5-1 percent of the sandweight and an amount of CTLA hydrocarbon polymer oil correspondinglyequal to 0.5-0 percent of the sand weight.

When an aqueous alkali metal silicate binder material is employed,suitability according to the foregoing test procedure can be achievedwith proportions of the binder material equal to 2-4 percent of theweight of the sand in the mix.

THE EMBODIMENT OF FIGS. 1-3

Referring to FIG. 1, the ingredients for the sand mix are supplied to asuitable continuous mixing apparatus and the mix so formed is dischargedonto an endless horizontal conveyor belt 1 which is driven stepwise tomove the upper run of the belt to the right, as viewed. Parallel sideplates 2 are provided, one extending along each side of the belt, insuch fashion that the upper run of the belt and the side platescooperate to form a trough effective to retain the sand mix. Ahorizontal scraper 3 extends between the side plates and is spaced abovethe upper run of the belt 1 to form the sand mix into a continuous bed 4of predetermined depth as the upper run of the belt advances.

In a location spaced from scraper 3 in the direction of movement of theupper run of the belt, a flat stationary back-up plate 5 is rigidlymounted beneath the upper run of the conveyor in a position such thatthe conveyor belt slides smoothly over the back-up plate in flushcontact therewith. In this location, there is mounted above the conveyora vertically acting rectilinear power device, such as a conventionalpressure operated motor 6 of the piston and cylinder type. A die,indicated generally at 7 and described hereinafter in detail, is rigidlymounted on the end of the piston rod 8 of motor 6. Operation of motor 6to drive the piston downwardly is effective to move die 7 downwardly,from an initial position spaced above the level of bed 4, until the diehas pressed the increment of bed 4 therebelow into the shape of thedesired mould part and has severed the mould part from the trailingportion of the bed.

Operation of conveyor 1 is carried out in timed relation to cyclicoperation of motor 6 so that, when die 7 is in its raised position, theconveyor presents a fresh increment of bed 4 and, while pressing iscarried out, the belt and therefore the bed are stationary. Once a mouldpart has been pressed and the die withdrawn upwardly, the next cycle ofmovement of conveyor 1 carries the shaped mould part away from thepressing station, the mould parts ultimately being delivered to acontinuously operated curing oven.

An important feature of the invention is that the pressing operation iscarried out in such fashion that each stroke of the pressing die,cooperating with the conveyor belt and back-up plate, forms thecorresponding portion of bed 4 into a complete mould part, by what is inessence a pressure moulding action, and also severs that mould part fromthe trailing bed. To accomplish this, a die having the construction seenin FIGS. 2 and 3 is employed. The die comprises a die plate 10 having aflat upper face to the center of which is welded an internally threadedbushing 11 for rigid connection of the die plate to the piston rod 12.The opposite face of the die plate presents the male pattern 13 to bepressed into the sand mix bed 4.

The plan shape of plate 10 is rectangular and the die plate is slidablyembraced by a rectangular confining and severing shroud 14. Shroud 14comprises four flat side members 15 welded together in rectangularfashion, the inner face of each member 15 being in flush slidableengagement with a different one of the edges of plate 10. Side members15 lie in vertical planes and the bottom edge of each side member isformed as a knife edge, at 16. Welded to the upper portions of twoopposite side members 15, so as to be above the die plate, are two bars17 each provided near its respective ends with two plain upright bores18, so that there is one bore 18 near each corner of the assembly. Bores18 freely accommodate, respectively, four screws 19, the threaded endsof which are engaged in upwardly opening bores in die plate 10.Compression springs 20 are provided, each surrounding a different one ofscrews 19 and engaged between the head of the screw and the upper faceof the corresponding bar 17.

When the die is raised out of engagement with bed 4, springs 20 urgescrews 19, and therefore die plate 10, upwardly so that the upper faceof the die plate .[.engates.]. .Iadd.engages .Iaddend.the lower faces ofbars 17. The pattern 13 is therefore spaced a significant distance abovethe lower cutting edges 16 of side members 15. When the die is drivendownwardly into bed 4, the side members 15 are forced completely throughthe bed, stopping only when engaged with the portion of belt 1 supportedby plate 5. Movement of the piston rod downwardly still continues, sothat die plate 10 is forced against the bed 4 with pattern 13 creatingthe desired moulded impression. Such downward movement of thecombination of the piston rod can be limited by a stop or stops (notshown) provided on the piston rod or on screws 19. When the piston rodagain moves upwardly to withdraw the die to its inactive position, themould part M is left on belt 1, completely severed from the bed 4, thecavity portion, sides and top of the mould part being completelypressure formed by the action of the die.

Considering FIG. 2, it will be seen that two opposite side members 15 ofthe die lie in vertical planes which extend along the inner faces of therespective side plates 2 of the apparatus, so that these sides of thedie are essentially in sliding contact with side plates 2 when the dieengages bed 4. Thus, for practical purposes, once the shroud 14 isforced downwardly into contact with belt .[.1.]. .Iadd.4.Iaddend.,shroud 14 cooperates with belt 1 and die plate 10 to completely confinesubstantially the entire increment of bed 1 disposed at the formingstation. The action at the forming station thus comprises severing thatincrement from the trailing portion of the bed, confining the severedincrement of the bed, and then completing the pressing operation byfurther movement of the die plate, with upward withdrawal of the diethen leaving the shaped mould part as an independent article ready to bemoved away from the pressing location by the next step of movement ofthe conveyor belt.

Excellent results are obtained with most mix formulations according tothe invention when the forming operation is carried out with a die platepressure, that is, the pressure applied to the sand mix bed 4 by plate10, on the order of 30 p.s.i., with pressures in the range of 10-100p.s.i., being useful.

It will be understood that springs 30 can be replaced by individualfluid pressure operated power devices.

In this embodiment, conveyor 1 is arranged to deliver the formed mouldparts M directly to a conventional curing oven of any suitable type.

THE EMBODIMENTS OF FIGS. 4-6

The embodiment shown in FIG. 4 comprises a conveyor having an endlessbelt 21, the conveyor being driven to cause the upper run of the belt tomove step-by-step along a horizontal path which passes first beneath asurge hopper and under a horizontal leveling scraper 23, thence througha pressing station where the die 27 and driving motor 26 are located,and then through a curing station embodying a stationary vacuum box 30,located below the upper run of the conveyor belt, and a verticallymovable curing box 31 which is located above the upper run of theconveyor belt.

The surge hopper and scraper 23 coact to form a continuous bed 24 of thesand mix, the bed being of predetermined depth. Die 27 is constructed inthe fashion earlier described with reference to FIGS. 2 and 3 and,therefore, has an effective length l, i.e., the dimension lengthwise ofthe belt between the two cutting edges 16, FIG. 3, of the walls of thesevering shroud 14, FIG. 3, which are transverse with respect to thebelt. Belt 21 is driven in equal steps, with each step equal to thelength l. Movable curing box 31 is of elongated rectangular planconfiguration and has an open side directed toward the belt, the openside being defined by side walls 32 and end walls 33 and 34, the latterextending transversely relative to the upper run of the belt. End wall32 is spaced from the adjacent wall of shroud 14, FIG. 3, by a distance(l) (x), with x being equal to one in the embodiment shown in FIG. 4.The space between end walls 33 and 34 is (l) (y), with y being equal to3 in the embodiment shown in FIG. 4.

Vacuum box 30 has a flat top wall 35 over which the upper run ofconveyor belt 21 slides, wall 35 being provided with a plurality ofspaced perforations (not shown). Curing box 31 is arranged above theupper run of conveyor belt 21 for vertical movement toward and away fromthe belt. Box 31 is driven by a vertically acting fluid pressureoperated rectilinear power device 36 of the piston and cylinder type.Power devices 26 and 36 are conventionally arranged for simultaneousoperation under the control of a sequencing control 37, so that thecuring box 31 is driven downwardly into engagement with the upper run ofbelt 21 simultaneously with each downward pressing stroke of die 27 andis raised above the path of travel of the pressed mould parts Msimultaneously with each upward movement of die 27. Each pressing strokeof die 27 forms and severs from bed 4 one mould part M, that mould partbeing carried toward curing box 31 by the next step of movement of theconveyor belt, which movement occurs during the succeeding upstroke ofthe die. After two mould parts M have been formed and severed by twosuccessive pressing strokes of die 27, the next upstroke of the die(with curing box 31 moving upwardly simultaneously with the die) will beaccompanied by advance of the two mould parts by one distance l,bringing the first mould part M just beyond the vertical plane occupiedby end wall 33. Accordingly, when the next pressing stroke of the dieoccurs, and curing box 31 is lowered to bring the lower edges of walls32-34 into engagement with the upper run of the conveyor belt, curingbox 31 will enclose the first mould part M. As the next two pressingstrokes occur, that mould part will be advanced through two more stepsand will therefore be adjacent end wall 34 of the curing box when,during the second of those two pressing strokes, the curing box islowered to engage the conveyor belt. At this point, three of the mouldparts M are enclosed by the curing box, one of those for the first time,the next for the second time, and the third for the third time.Thereafter, each time the curing box descends as die 27 forms and seversa new mould part, there will be three mould parts within the confines ofthe curing box.

The interior of curing box 31 is connected via conduit 38 to one port ofa conventional fast-acting power operated multi-way valve 39, anotherport of the valve being connected via conduit 40 to a vacuum chamber 41evacuated by vacuum pump 42, and still another port of the valve beingconnected via conduit 43 to a source 44 of carbon dioxide underpressure. The interior of vacuum box 30 is connected via conduit 45 andcheck valve 46 to conduit 38, with check valve 46 oriented to allow flowonly from the interior of vacuum box 30 to conduit 38. Valve 39 is soarranged as to be operable through a sequence in which (a) conduit 38 isfirst connected to conduit 40, and hence to the vacuum chamber, whileconduit 43 is sealed off; (b) conduit 38 is then connected to conduit43, and hence to carbon dioxide source 44, while conduit 40 is sealedoff; (c) conduit 38 is then vented to the atmosphere, with conduits 40and 43 both sealed off; and (d) all of conduits 38, 40 and 43 are sealedpreparatory to repeating the sequence. Automatic sequencing controlsystem 37 is constructed and arranged to accomplish simultaneousoperation of power devices 26 and 36 and to cause valve 39 to operatethrough the sequence just described in response to lowering of curingbox 31 into sealed engagement with the upper run of the conveyor belt.Thus, when the curing box engages the conveyor belt, valve 39 connectsconduit 38 to vacuum chamber 41, and the curing box is evacuated. Sincecheck valve 46 allows fluid flow from vacuum box 30, that box isevacuated simultaneously with evacuation of curing box 31. This step ofthe sequence is accomplished in a time which is short in comparison tothe total time during which the curing box engages the conveyor belt,and the purpose of this step is to evacuate the curing box and the mouldparts M enclosed thereby, and to evacuate box 30 so that there will notbe a significant pressure differential across the thickness of theconveyor belt and the portion of the belt under the curing box willtherefore not tend to be drawn into the curing box.

The next step in the sequence of operation of valve 39 then occurs,causing carbon dioxide gas to fill the curing box 31 and to fill theinterstices of the mould parts M, with the result that the aqueoussodium binder content of each mould part is completely cured throughoutthe mould part and the mould part thus rigidified. Valve 39 remains inits second step position for a major portion of the total time periodduring which the curing box engages the conveyor belt.

Just before the upstroke of power device 36 occurs to raise curing box31 from its mould-part-confining position, valve 39 is operated throughthe third step of its sequence, connecting the interior of the curingbox to the atmosphere via conduit 38 so that the pressurized carbondioxide within the curing box is vented and there will be no significantoutrush of gas at the conveyor belt as the curing box is disengaged fromthe belt. Finally, valve 39 is operated to its fourth, or fully closedposition, as curing box 31 is raised to the upper limit of its travel.

Advantageously, the surge hopper 47 is equipped with a sliding gate 48actuated by a power device 49 from full closed to full open position,the power device 49 being controlled to open gate 46 each time apressing cycle occurs.

FIG. 5 illustrates a modified form of the apparatus of FIG. 4 whereinthe curing box 31 is mechanically joined with the forming die 27. Here,transverse wall 15a is common to both the shroud 14 of the forming dieand the curing box, so that the space (l) (x), FIG. 4, between theforming die and the curing box is eliminated.

Another embodiment, illustrated in FIG. 6, provides for simultaneousproduction of both the cope and the drag for a complete mould. Here, theapparatus includes an additional press unit, comprising power device 26aand die 27b, located downstream of and immediately adjacent to the powerdevice 26 and die 27. Under control of the sequencing control device 37the two press units are operated concurrently, so that die 27a forms andsevers an additional mould part each time a mould part is formed andsevered by die 27. Die 27 can be equipped with a pattern suitable forthe cope, and die 27a can be equipped with a pattern suitable for thedrag. The two patterns have the same dimension lengthwise of theconveyor, and the conveyor is driven stepwise with the length l of eachstep equal twice the effective length of one pattern. In thisembodiment, the curing box has a length (l) (y), where y equals two, sothat the curing box encloses four mould parts each time the box engagesthe belt during a pressing operation. Box 31 is spaced from die 27a by adistance (l) (x), where x equals one. Accordingly, during continuousoperation of the apparatus, there are always two mould parts on theportion of the conveyor between die 27a and curing box 31, and these twoparts include a cope M, formed and severed by die 27, and a drag M',formed and severed at the same time by die 27a.

THE EMBODIMENT OF FIGS. 7-20

FIGS. 7-20 illustrate in more detail a particularly advantageousembodiment of the apparatus having the general configurationhereinbefore described with reference to FIG. 4. The apparatus comprisesan elongated horizontal frame 50 which supports an endless belt conveyor51 and can be considered as defining a sand mix supply station S, at theinfeed end of the conveyor, a forming station P, located downstream fromthe supply station, and a curing station C, located between the formingstation and the discharge end of the conveyor.

FRAME STRUCTURE

Frame 50 includes four floor-mounted uprights 52 to which the sideplates 53 are secured to support the take-up blocks 54 for the tailpulley or roller 55 of conveyor 51. At station S, the frame includes anupright floor-mounted base, indicated generally at 56, for the press 57,base 56 comprising four legs 58 disposed so that each leg defines onecorner of the square plan of the base, the tops of the legs beinginterconnected by horizontal members 59, and additional sets ofhorizontal brace members 60 being provided therebelow. A rigid pressurepad, in the form of a square metal plate 61 of substantial thickness, isfixed to the top of base 56, as by being attached directly to members 59by screws.

Two longitudinal side beams 62 interconnect the respective adjacentpairs of uprights 52 and legs 58, one end of each beam 62 beingsupported directly on the corresponding upright 52, the other end ofeach beam being supported by a transverse plate 63. Beams 62 are ofU-shaped transverse cross-section, arranged with the base of the Uvertical and the webs which form the legs of the U projecting outwardlyaway from the base, the two beams being identical and the upper websthereof lying in a common horizontal plane which is slightly below thehorizontal top surface of pressure pad 61. Downstream of forming sectionP, frame 50 comprises two side beams 65 which extend between and aresecured to the appropriate pair of legs 58 of the press base 56 and theside plates 66 in which the head pulley or roller 67 of conveyor 51 isjournalled, beams 65 being interconnected by transverse members 68 andsupported by two pairs of legs 69.

Frame 50 includes means supported by beams 62 and 65, and coating withpressure pad 61 and a pressure pad, later described, at the curingstation, for providing rigid support beneath and through essentially theentire extent of the upper run of the endless belt 68 of conveyor 51. Aswill be clear from FIGS. 8 and 9, a side strip 69 is welded to andextends longitudinally along the top of each beam 62, and a longitudinalcenter strip 70, secured at its respective ends to plate 63 and anappropriate transverse member at side plates 53, extends for essentiallythe full distance from the tail pulley to the press. A plurality ofsupport bars 71, of L-shaped transverse cross-section, are arranged in"herringbone" fashion and secured to side strips 69 and center strip 70.Thus, bars 71 are arranged in pairs, with the bar of each pairconverging inwardly and toward forming station P, the outer end of eachbar being welded to the corresponding side strip 69 and the inner end tocenter strip 70. Each bar 71 has one web of its "L" horizontal, with theother web of the " L" depending therefrom, the upper faces of thehorizontal webs of all of the bars lying in the horizontal planeoccupied by the upper face of pressure pad 61. As seen in FIG. 8, thebars 71 are spaced apart lengthwise of the apparatus so that, while thehorizontal webs of bars 71 coact to provide a rigid horizontal supportover which the conveyor belt can slide, spaces 72 are provided forescape of sand, etc., which would otherwise collect and impair operationof the conveyor.

Between forming station P and curing station C, support for the upperrun of the conveyor belt is provided by a plurality of bars 73, FIGS. 8and 10, secured to side strips 74 and center strip 75 in the generalfashion just described with reference to bars 71, the arrangement beingthe same as for bars 71 save that the spaces between bars 73 aredistinctly smaller than the spaces between bars 71. Support bars 76,FIG. 8, are provided in the space between curing station C and headpulley 67 in the same fashion just described with reference to bars 73.The upper faces of the horizontal webs of all of the bars 73, 76 lie ina common plane coincident with the upper faces of pressure pad 61 andthe pressure pad of the curing station.

CONVEYOR AND CONVEYOR DRIVE

Conveyor 50 includes an endless flexible impervious belt 77 whichextends around tail pulley 55 and head pulley 67 under tension, thehorizontal upper run of the belt extending from the tail pulley intoimmediate sliding engagement with the horizontal webs of support bars71, then over pressure pad 61, then over the horizontal surfaces ofsupport bars 73, thence across the pressure pad at curing station C, andover the horizontal surfaces of support bars 76 to head pulley 67. Asupporting idler roller 78 is engaged beneath the lower run of theconveyor belt at its midpoint, roller 78 being suitably suspended frombeams 65.

The conveyor is driven in stepwise fashion by a rectilinear power device79, FIG. 11, which can be of conventional hydraulic piston-and-cylindertype. The blind end of cylinder 80 of power device 79 is pivotallyconnected to a mounting bracket 81 secured to the frame, the pivotalaxis being parallel to and below the axis of rotation of head pulley 67.Piston rod 82 of the power device 79 projects toward the location of thehead pulley and is pivotally connected by a clevis 83 to a nut 84 whichis secured to crank arm 85 by an adjusting screw 86 extending lengthwiseof the arm, so that the screw and nut coact as a means for adjusting theeffective length of the crank arm. Crank arm 84 is connected to drivehead pulley 67 through a conventional one-way clutch (not shown) sooriented that when piston rod 82 is retracted, swinging crank arm 85counterclockwise (as viewed in FIG. 11), an increment ofcounterclockwise movement of head pulley results. No movement isimparted to the head pulley when, as piston rod 82 is extended, crankarm 85 is swung in a clockwise direction. The increment of rotationimparted to the head pulley by each cycle of operation of power device79 drives conveyor belt 77 to cause the upper run of the belt to advanceone step from the tail pulley toward the head pulley, the length of thestep being the same for each cycle of operation of power device 79 andbeing predetermined by adjustment of screw 86. Completion of eachincrement of rotation of the head pulley, and thus of each step ofmovement of the conveyor belt, is detected by a position switch 87operated by crank arm 85. Stationary condition of the conveyor belt issensed by a position switch 88 operated by crank arm 85. Switches 87, 88provide controlling inputs to the sequencing control device, e.g.,device 37, FIG. 4, in conventional fashion.

MEANS FOR ESTABLISHING BED OF SAND MIX ON CONVEYOR 51

Adjacent tail pulley 55, the apparatus includes a hopper indicatedgenerally at 89 and to which the sand mix is supplied from aconventional continuous mixer (not shown). Hopper 89 includes adischarge throat 90 of rectangular transverse cross-section, throat 90being equipped with mounting flanges 91, FIG. 12, which project acrossand are bolted to side beams 92 of a horizontal supporting frame 93.Frame 93 is located above tail pulley 55 and the adjacent portion of thehorizontal upper run of conveyor belt 77, and is mounted on frame 50 byfour conventional vertical jacking devices 94 which are operative tosupport the hopper with the terminal edges of the walls of throat 90lying in a horizontal plane spaced a predetermined distance above theupper run of the conveyor belt.

The side beams 92 of frame 93 are interconnected at one end by a crossmember 96. Each beam 95 carries two series of rollers 97, the rollersbeing mounted at the inner sides of the beams to rotate about parallelaxes which extend across the line of travel of the conveyor belt, thetwo series of rollers being spaced apart vertically to accommodate aflat horizontal gate 98 of rectangular plan form, the rollers of oneseries engaging the upper face of the gate at one edge thereof while therollers of the other series engage the opposite face of the gate at thesame edge. Two rectilinear power devices 99, typically of the hydraulicpiston-and-cylinder type, are mounted on frame 93, the cylinders 100thereof being rigidly secured to cross-beam 96 and an additionaltransverse member 101, and the piston rods 102 extending mutuallyparallel and parallel to the line of travel of the conveyor belt, towardgate 98. The free ends of rods 102 are secured to a flange 103 fixed tothe edge of the gate which is nearer the power devices 99. Thearrangement is such that operation of the power devices to projectpiston rods 102 moves gate 98 to a position closing throat 90 of thehopper, and retraction of the piston rods withdraws the gate to allowsand mix to flow by gravity onto the upper run of the conveyor belt.

As the conveyor belt is moved, the edge of the side wall of throat 90which is nearer forming station P acts as a scraper to level the bed ofsand mix in the same manner as does levelling scraper 3, FIG. 1. Betweenhopper 89 and forming station P, side beams 62 support adjustable sideplates 104 which define the respective edges of the sand mix bed carriedby the upper run of the conveyor belt.

FORMING PRESS 57

Press 57 comprises a heavy support plate 105 rigidly mounted on pressurepad 61 by four elongated vertical posts 106 which also serve as guidesfor the die plate 107 and the shearing shroud 108. The bottom ends ofposts 106 are shouldered against and extend downwardly through openingsin the respective corners of pressure pad 61 and are secured by nuts atthe bottom face of the pressure pad. A main, heavy duty hydrauliccylinder 109 is mounted on plate 105 at the center of the plate andprojects thereabove, the piston rod 110 for cylinder 109 passingdownwardly through a central opening in plate 105 and being rigidlysecured to the center of die plate 107. Spaced each on a different sideof cylinder 109 and lying in the same plane as the longitudinal centerline of conveyor 51 are two smaller hydraulic cylinders 111 and 112,these cylinders also being rigidly secured to and projecting upwardlyfrom plate 105. The piston rods 113 and 114 for cylinders 111 and 112,respectively, extend downwardly through appropriate openings in plate105, each piston rod 113, 114 extending along a vertical line midwaybetween a different pair of the posts 106. Piston rods 113, 114 passfreely through .[.appropritate.]. .Iadd.appropriate .Iaddend.openings indie plate 107 and the lower ends of the piston rods are secured toshearing shroud 108 as later described.

Die plate 107 comprises a main rectangular body plate 115 provided ateach corner with a cylindrical slide bearing 116 which embraces one ofthe posts 106. The male pattern 117 for the mould part is detachablymounted on plate 115 by a mounting plate 118 in any of the suitablemanners well known in the stamping press art.

Shearing shroud 108 is made up of four flat side plates secured rigidlytogether to form an open rectangle, the .[.conveyor.]. .Iadd.plates.Iaddend.119 and 120 extending lengthwise of the conveyor 51 in thecompleted apparatus, and plates 121 and 122 extending transversely ofthe conveyor, the dimensions of the plates being such that the shroudcan slidably embrace mounting plate 118. In thie regard, .[.gears,.].inner faces of plates 119-122 are smooth, flat and uninterrupted. In thecompleted apparatus, the lower edges of all of plates 119-122 lie in acommon horizontal plane, and these edges are formed as blunt knife edgesto reduce resistance as the shroud is forced downwardly into the bed ofsand mix. Plates 121, 122 are of greater vertical dimension than areplates 119, 120 so that plates 121, 122 project above the upper edges ofplates 119, 120 for a substantial distance to present flange portions121a and 122a, respectively. Mounting members 123 and 124 are secured tothe outer faces of flange portions 121a and 122a, respectively, eachmounting member being of L-shaped transverse cross-section and arrangedwith one web of the L overlying the respective flange portion and theother web of the L projecting horizontally therefrom. Two verticalplates 125 are welded to the central portion of each member 123, 124 andare spaced apart to accommodate a pivot block 126 fixed to the lower endof the corresponding piston rod 113, 114. For each piston rod 113, 114 apivot pin 127 extends through the plates 125 and block 126 to secure theshroud 108 to the piston rods 113, 114.

As best seen by comparing FIGS. 15 and 16, four additional members 128are secured to and extend vertically between the corresponding cornersof pressure pad 61 and support plate 105. Members 128 are of L-shapedtransverse cross-section and, as shown in FIG. 16, embrace therespective corners of pad 61 and plate 105. For the two of members 128nearer tail pulley 55, one web of the L of each member is transverse tothe conveyor and faces the tail pulley. For the other two of members128, the webs of the L which are transverse to the conveyor face headpulley 67. A rack bar 129, FIGS. 14 and 15, is welded to such transverseweb of each member 128, the rack bars being vertical and their teethfacing lengthwise of the conveyor. At each of its ends, each member 123,124 has secured thereto a bracket 130, FIG. 16, on which is mounted apillow block 131. The pair of pillow blocks 131 carried by member 123rotatably support a horizontal shaft 132 which extends transversely ofthe conveyor. A shaft 133 is similarly carried by the pillow blocks 131mounted on member 124. Each end of each shaft 132, 133 has fixed theretoa pinion 134, FIGS. 15 and 16, the pinions 134 being operatively meshedwith the respective rack bars 129. With shroud 108 and support members123, 124 constituting a rigid assembly, the combination of shafts 132,133 and their pinions 134 coact with rack bars 129 to assure that thecommon plane of the bottom, knife-like edges of plates 119-122 of theshroud is maintained horizontal as the shroud is actuated by the powerdevices 111 and 112.

The sequencing control device employed with the apparatus, e.g., controldevice 37, FIG. 4 causes the press 57 to complete one cycle each timeconveyor belt 77 has been advanced by one step. During each cycle of thepress, power devices 111, 112 are first operated to drive the shearingshroud 108 downwardly until, as seen in FIGS. 14 and 15, the shroudengages the upper run of the conveyor belt 77 and forces the sameagainst the support afforded by pressure pad 61. Such movement of shroud108 causes plate 121 thereof to shear completely through the bed of sandmix, and a predetermined quantity of the sand mix is thus confined bythe coacting shroud and conveyor belt. When the shroud engages theconveyor belt 77, power device 109 is operated to drive die plate 107downwardly a predetermined distance adequate to cause pattern 117 tocompress the confined body of sand mix into the shape desired for themould part. With die plate 107 remaining in its lowered position, stillin pressure engagement with the now-shaped mould part, power devices111, 112 are then operated to raise shroud 108 to the limit of itsupward travel, so that the shroud is spaced well above the surface ofthe bed of sand mix carried by the conveyor Power device 109 is thenoperated to raise die plate 107 to its upper most position, leaving theshaped mould part in place on belt 77. The next step through which belt77 is driven conveys the mould part away from the press and brings a newportion of the bed of sand mix into position for the next cycle ofoperation of the press.

STRUCTURE AT CURING STATION C

The mould parts formed by press 57 are advanced by conveyor belt 77toward station C, adjustable side plates 140 being mounted on side beams65 to assure that the mould parts remain centered on the belt. Atstation C, the apparatus includes a heavy flat rectangular plate 141,FIG. 17, which extends across and is secured to the upper edges of sidebeams 65 to serve as the top of a fixed vacuum box 142 and as thepressure pad to oppose the downward force applied to the upper run ofthe conveyor belt by a vertically movable curing box 143.

Vacuum box 142 is a simple rectangular structure formed from flat sideand end plates which are welded to and depend from plate 141, and a flatbottom plate welded to the bottom edges of the side and end plates.Plate 141 is provided with a plurality of perforations 144, FIG. 17,which extend .[.compeltely.]. .Iadd.completely .Iaddend.through theplate and communicate with the interior of the vacuum box, the entireperforated area of plate 141 being covered by the upper run of theconveyor belt. A fitting 145 is provided on the bottom wall to connectthe interior of the vacuum box to an evacuated chamber and vacuum pumpin the manner earlier described with reference to FIG. 4.

Curing box 143 comprises rectangular side plates 146 and 147,rectangular end plates 148 and 149, and a rectangular top plate 150, allwelded together to define a chamber which is open at the bottom, has awidth slightly less than that of conveyor belt 77, and is elongatedlengthwise of the conveyor. A longitudinal side beam 151 extends alongthe outer surface of plate 146 and is welded thereto. A beam 152 issimilarly secured to plate 147. The ends of beams 151, 152 projectbeyond the respective end plates 148, 149 and are each provided with aslide bearing 153, the bearings 153 each slidably embracing a differentone of four vertical guide posts 154 which are each rigidly secured toand extend upwardly from a different corner portion of plate 141. Posts154 are of equal height and are rigidly interconnected at their upperends by longitudinal members 155 and transverse members 156.

Four hydraulic cylinders 157 are mounted on and depend vertically fromplate 141, the plate being provided with openings through which thepiston rods 158 for the cylinders project upwardly. The upper ends ofpiston rods 158 carry pivot blocks connected to clevises 159 secured tothe lower edges of beams 151 and 152. The longitudinal members 155 carrytwo pairs of pillow blocks 160 with the pillow blocks of each pair beingaligned transversely across the structure to rotatably support twoshafts 161. A third shaft 162 extends lengthwise of the curing boxbetween shafts 161, being carried by bearings supported on one of themembers 155. Each shaft 161 is equipped with a bevel gear, and bevelgears are fixed to the ends of the shaft 162 to mesh with those onshafts 161 so that shafts 161 must rotate in unison. Four vertical posts163 are secured to and project upwardly from top plate 150 of curing box143, two of posts 163 being near one of the shafts 161 and the other twoposts being near the other shaft 161. Each post 163 carries a verticalrack bar 164 so disposed that its teeth face the corresponding shaft161. Each shaft 161 carries two pinions 165 and each pinion 165 ismeshed with one of the rack bars 164.

Curing box 143 is a rigid unit disposed with the bottom edges of itsside and end plates lying in a common plane. Guide posts 154, slidebearings 153 and beams 151, 152 support the curing box for verticalmovement between an upper position, in which the box is spaced above theupper run of belt 77 by a distance adequate to allow free passage of themould parts as the belt advances, and a lower position, in which thelower edges of the side and end plates of the box engage the upper runof the conveyer belt and the latter is, in effect, a bottom wall for thebox. Hydraulic cylinders 157 are operable to drive the curing boxbetween its two extreme positions, selectively in both directions. Thecombination of shafts 161, 162 and their respective bevel hears, pinions165 and rack bars 164 assures that precise horizontal disposition of thecuring box 143 will be maintained throughout its upward and downwardmovement.

Four lock-down devices 167 are provided to urge the bottom edges of theside and end plates of the curing box into fluid-tight sealingengagement with the upper run of the conveyor belt when the curing boxis in its lowermost position. Each device 167 includes a horizontalhydraulic cylinder 168 mounted on plate 141 and arranged to move itspiston rod toward and away form the curing box. The piston rod for eachcylinder 168 is equipped with a cam block 169 having a lower face whichslants upwardly and away from the hydraulic cylinder. In appropriatepositions each operatively disposed with respect to a different one ofcylinders 168, four horizontal pins 170 are mounted on the outer sidesof side plates 146 and 147, the arrangement being such that simultaneousoperation of the cylinders 168 causes the cam blocks 169 to ride up andover the respective pins 170, forcing the curing box downwardly so thatthe edges of plates 146-149 indent the conveyor belt in sealing fashion,with that condition being preserved until cylinders 168 are operated toretract the piston rods.

A header pipe 175 extends beside and is mounted on one of thelongitudinal members 155. Header 175 has a central fitting 176, to beconnected to a pipe which can be placed in communication selectivelywith an evacuated chamber and a source of compressed carbon dioxide gas,as earlier described with reference to FIG. 4. Header 175 also has twofittings 177, spaced equally from fitting 176, which are each connectedto a different one of two flexible hoses 178. Two fittings 179 areprovided on top plate 150 of the curing box, each of hoses 178 beingconnected to a different one of fittings 179 to place header 175 incommunication with the interior of the curing box. Fitting 145 of vacuumbox 142 can be connected via suitable piping (not shown) to header 175,a check valve being provided as earlier described with reference to FIG.4 to allow the header to communicate with the vacuum box only in anevacuating mode.

Plate 141 and curing box 143 are so located relative to press 57 andoperation of cylinders 157 is so timed relative to stepwise movement ofconveyor belt 77 that, when the apparatus is in full operation, the endplates 148, 149 of the curing box will enter the spaces between adjacent.[.moult.]. .Iadd.mould .Iaddend.parts each time the curing box islowered. It will be apparent that the fluid circuit and the valvingsequence described with reference to FIG. 4 can be employed toaccomplish evacuation, carbon dioxide curing, and venting during eachcycle of operation of press 57, all as earlier described, and thatevacuation of box 142 simultaneously with evacuation of the curing box143 will assure that the upper run of the conveyor belt will remain flatagainst plate 141 during the evacuating step.

What is claimed is:
 1. In an apparatus for high speed production of foundry mould parts from a curable sand mix having adequate plastic flowability for pressure moulding, the combination ofan endless horizontal conveyor extending from a mix depositing station to a forming station; means at the mix despositing station for depositing the sand mix on the conveyor and forming the deposited mix into a bed of predetermined depth; .Iadd.drive .Iaddend.means connected to said conveyor to drive the same stepwise to advance the bed of sand mix from the depositing station to the forming station in steps of equal length; a press unit located at the forming station and comprisinga flat support operatively arranged with respect to said conveyor to rigidly support against downward movement the portion of the bed of sand mix presented at the forming station by stepwise advance of the conveyor, a pattern carrier, .[.a bed severing device, and.]. .Iadd.a combination shroud and bed severing device, and .Iaddend. vertically acting power means connected to said pattern carrier and said .Iadd.combination shroud and .Iaddend.bed severing device to drive the same downwardly toward said flat support and to return the same upwardly to positions adequately spaced above said conveyor to allow unimpeded movement of said bed of sand mix at the forming station, said .[.bed severing device inclusing a portion which extends transversely of the conveyor in a position to sever from the trailing portion of the bed a portion of the bed adequate for the mould part to be formed..]. .Iadd.combination shroud and bed severing device comprising two flat mutually parallel wall members extending transversely of said conveyor and spaced apart by a distance such that the edges of said wall members which are directed toward the conveyor are separated by a distance substantially equal to the length of said equal steps through which the conveyor is driven, the one of said two wall members which is nearer the mix depositing station being operative as a severing device to sever from the trailing portion of the bed a portion of the bed adequate for the mould part to be formed, .Iaddend. said power means being capable of operation, in response to completion of a step of movement of the bed by said conveyor, to drive said .Iadd.combination shroud and bed .Iaddend.severing device downwardly into engagement with the conveyor.Iadd., whereupon the severed portion of the bed is laterally confined by said combination shroud and bed severing device, .Iaddend.and to drive said pattern carrier downwardly to press the severed portion of the sand mix into the shape determined by a pattern carried by said pattern carrier. .[.2. The combination according to claim 1, wherein said pattern carrier is of rectangular plan configuration and is so arranged that two sides thereof are transverse to said conveyor; and said bed severing device comprises four severing elements arranged to define a hollow rectangle of such size and configuration that said pattern carrier, and the pattern carried thereby, can move vertically within and independently of said bed severing device..]. .[.3. The combination according to claim 2, wherein said power means is a single power device connected to drive said pattern carrier; and said bed severing device is mounted on said pattern carrier by means including a yieldable connection operative to allow said pattern carrier to continue its downward movement after said bed shearing device has engaged said conveyor..].
 4. The combination according to claim .[.2.]. .Iadd.1 .Iaddend.wherein said power means comprisesa first power device connected to said pattern carrier, and power means, in addition to said first power device, .Iadd.comprising at least one power device .Iaddend.connected to said .Iadd.combination shroud and .Iaddend.bed severing device, said pattern carrier and said .Iadd.combination shroud and .Iaddend.bed severing device being mounted for vertical movement independently of each other.
 5. The combination defined in claim 4, wherein said additional power means includes two power devices each connected to a different one of .Iadd.said .Iaddend.two mutually parallel .[.ones of said severing elements.]. .Iadd.wall members. .Iaddend. .[.6. The combination defined in claim 1, wherein said conveyor extends beyond said forming station,each step of operation of said conveyor being effective to remove from the forming station the mould part formed by the preceding cycle of operation of said press as well as to advance the leading end portion of the sand mix bed into operative position at the forming station..].
 7. The combination defined in claim .[.6.]. .Iadd.1 .Iaddend.whereinsaid conveyor comprises an endless belt, the horizontal upper run of which extends from the forming station through a curing station, the combination further including a flat support member located at the curing station and over which the upper run of the conveyor belt extends; means located above said conveyor at the curing station and defining a curing chamber, said means comprising,a rigid top wall, two rigid mutually parallel side walls, and two rigid mutually parallel end walls, said side walls being spaced apart by a distance smaller than the width of the conveyor belt, said end walls being spaced apart by a distance equal to a multiple of the length of each step of advance of the conveyor, the lower edges of said side and end walls defining an open bottom for said curing chamber; means mounting said curing chamber for vertical movement between a raised position, in which the lower edges of said side and end walls are spaced above the conveyor to allow free passage of mould parts through the curving station, and a lower position, in which the lower edges of said plates engage said conveyor belt in fluid-tight sealing fashion in opposition to said flat support member,said curing member being so positioned lengthwise of said conveyor that, when said curing chamber is moved into engagement with the conveyor belt at a time between steps of movement of the conveyor belt, said end walls will enter the respective spaces between adjacent pairs of moulded parts and a plurality of mould parts will be enclosed in said curing chamber; power means for moving said curing chamber between said two positions; and means for introducing a curing gas under pressure into said curing chamber when said side walls and end walls engage said curing chamber.
 8. The combination defined in claim 7 and further comprisingreleasable lock-down means operatively arranged to lock said curing chamber against the combination of the conveyor belt and said support member.
 9. The combination defined in claim 7 and further comprisingmeans for evacuating said curing chamber, and the mould parts enclosed therein, prior to introduction of the curing gas.
 10. The combination defined in claim 7, wherein said .Iadd.combination shroud and .Iaddend.bed severing device comprises four flat severing plates arranged to define a hollow rectangle of such size and shape as to surround said pattern carrier,one end wall of said curing chamber serving as one of said severing plates. 